Impulse noise management

ABSTRACT

Evaluation of the impact of impulse noise on a communication system can be utilized to determine how the system should be configured to adapt to impulse noise events. Moreover, the system allows for information regarding impulse noise events, such as length of the event, repetition period of the event and timing of the event, to be collected and forwarded to a destination. The adaptation can be performed during one or more of Showtime and initialization, and can be initiated and determined at either one or more of a transmitter and a receiver.

RELATED APPLICATION DATA

This application is a Continuation of U.S. application Ser. No.12/769,193 filed Apr. 28, 2010, now U.S. Pat. No. 8,462,835, which is aContinuation of U.S. application Ser. No. 10/597,482, filed Jul. 27,2006, now abandoned, which is a national stage application under 35U.S.C. 371 of PCT Application No. PCT/US2005/006842, filed Mar. 3, 2005,which claims the benefit of and priority under 35 U.S.C. §119(e) to U.S.Provisional Application No.: 60/549,804, entitled “On-Line Impulse NoiseProtection (INP) Adaptation,” filed Mar. 3, 2004, and U.S. ProvisionalApplication No.: 60/555,982, entitled “Impulse Noise Protection (INP)Training,” filed Mar. 24, 2004, each of which are incorporated herein byreference in their entirety.

BACKGROUND

1. Field of the Invention

This invention generally relates to communication systems. Inparticular, an exemplary aspect of this invention relates to impulsenoise protection adaptation. Another exemplary aspect of this inventionrelates to impulse noise length and period determination and use thereoffor impulse noise protection adaptation.

2. Description of Related Art

Communications systems often operate in environments that produceimpulse noise. Impulse noise is a short-term burst of noise that ishigher than the normal noise that typically exists in a communicationchannel. For example, DSL systems operate on telephone lines andexperience impulse noise from many external sources includingtelephones, AM radio, HAM radio, other DSL services on the same line orin the same bundle, other equipment in the home, etc. It is standardpractice for communications systems to use interleaving in combinationwith Forward Error Correction (FEC) to correct the errors caused byimpulse noise. Standard initialization procedures in ADSL and VDSLsystems are designed to optimize performance (data rate/reach) in thepresence “stationary” crosstalk or noise. Impulse noise protection ishandled with interleaving and FEC, but the current xDSL procedure atleast does not provide specific states to enable training for theselection of the appropriate interleaving and FEC parameters.

An exemplary problem associated with traditional communication systemsis that they use traditional Signal to Noise Ratio (SNR) measurementtechniques to determine the SNR of the channel. These traditionaltechniques assume that the noise is stationary and does not containnon-stationary components such as impulse noise. The most common methodfor measuring the SNR is to calculate the mean-square error of thereceived signal based on a known transmitted signal, which is describedin the ADSL series of ITU G.992.x standards and the VDSL series of ITUG.993.x standards, which are incorporated herein by reference in theirentirety. These traditional methods for measuring SNR do not correctlymeasure the impact of impulse noise and do not have the noise capabilityto determine how the system should be configured to handle impulsenoise.

There has been proposed that there is a need in ADSL and VDSL systems toprovide robust error-free performance in the presence of high,real-world impulse noise. A specific proposal recommends that thestandard impulse noise protection (INP) values are extended to values of4, 8, 16 and 32 in order to handle high levels of impulse noise. Impulsenoise protection is defined in the ADSL2 Standard G.992.3, which isincorporated herein by reference in its entirety, as the number ofimpulse noise corrupted DMT symbols that can be corrected by the FEC andinterleaving configuration. Specifically, G.992.3 defines the followingvariables:

INP=½*(S*D)*R/N

S=8*N/L

Latency (or delay)=S*D/4

Line Rate (in kbps)=L*4

where N is the codeword size in bytes, R is the number of parity (orredundancy) bytes in a codeword, D is the interleaver depth in number ofcodewords, and L is the number of bits in a DMT symbol.

If K is the number of information bytes in a codeword then:N=K+Rand the user data rate is approximately equal to:L*4*K/N.

In general, DSL systems (such as the one defined in ADSL G.992.x or VDSLG.993.x) use the FEC and Interleaving Parameters (FIP) characterized bythe set of parameters (N, K, R, D). Using these parameters, the BurstError Correction Capability (BECC) in bytes can be simply calculated as:BECC=D*R/2 byteswhere BECC is defined as the number of consecutive byte errors that canbe corrected by the receiver. Note that if the receiver uses moreintelligent decoding schemes, such as erasure detection, it is possibleto correct even more than D*R/2 bytes. It also follows from above thatINP=BECC/L.

The proposal further recommends that the higher INP values are achievedby increasing the amount of FEC redundancy while keeping the same systemlatency and the same interleaver memory at the expense of user data rateor excess margin. Since, on phone lines without excess margin, there isclearly a trade-off between high impulse noise protection values anduser data rate, it would be advantageous to try to maximize the userdata rate by finding the minimum impulse noise protection value that canprovide adequate impulse noise protection. The current techniqueincludes the steps of an operator, or service provider, configuring theADSL connection with a specific noise protection value, the ADSLconnection is initialized and the transceivers enter into steady statedata transmission (i.e., Showtime), and if the connection is stable,i.e., error-free, then the service is acceptable and the process ends.If there are bit errors, then the process is repeated with the operator,or service provider, configuring the ADSL connection with anotherspecific INP value.

One exemplary problem with this approach is that it is time consumingand can result in sub-optimum user rates. This is illustrated withreference to the following examples:

EXAMPLE 1

Assume that for a particular DSL connection there is high impulse noiseand the required INP is 8. As a result, if the service provider uses afirst INP configuration of 2, the DSL connection will not be error free.Therefore, the service provider needs to configure a higher INP valueand reinitialize the connection. If a value of 4 is used as a second INPvalue, it still will not provide adequate impulse noise protection andbit errors will occur. Again, the service provider will need toconfigure a higher INP value until the correct value of 8 is configured.Clearly, the connection needs to be re-initialized every time there is anew INP configuration chosen and this trial and error technique provesto be very time consuming

EXAMPLE 2

Assume that for a particular DSL connection there is high-impulse noiseand the required INP is 4. As a result, if the service provider uses afirst INP configuration of 2, the connection will not be error free.Therefore, the service provider needs to configure a higher INP valueand reinitialize the connection. In order to save time and not gothrough the number of initializations has occurred in Example 1, theservice provider simply configures the system to the maximum INP valueof 32. Obviously, there will be no bit errors with INP=32 since thisconnection needs only an INP value of 4. As a result, user datathroughput is greatly degraded since the additional FEC redundancy willbe three times higher than what is actually needed. For example, if theINP of 4 requires 10 percent FEC redundancy, an INP of 32 requires 40percent FEC redundancy which results in a 30 percent decrease in userdata rate.

SUMMARY

In additional to the above drawbacks, the related systems do not havethe ability to actually measure the length or repetition period ofimpulse noise which can both be used to determine an appropriate impulsenoise protection setting.

Exemplary aspects of this invention relate to determining the impact ofimpulse noise on a communication system and the capability to determinehow the system should be configured to handle the impulse noise event.

An exemplary aspect of this invention determines the impact of impulsenoise by transmitting and receiving using a plurality of different FECand interleaving parameter settings. For each FEC and InterleavingParameter (FIP) setting, the received signal quality is determined by,for example, detecting if there are bit errors after the receiverperforms the FEC decoding and deinterleaving. Based on this, theappropriate FIP setting is selected and used for transmission andreception.

A plurality of FIP settings can be used for transmission and reception.In accordance with one particular aspect of this invention, the systemcan transition from one FIP setting to another FIP setting without goingthrough the startup initialization procedure such as the startupinitialization sequence utilized in traditional xDSL systems. Forexample, an xDSL system that implements the systems and methodsdescribed herein could start using an FIP setting of (N=255, K=247, R=8,D=64) and then transition to an FIP setting of (N=255, K=239, R=16,D=64) without re-executing the startup initialization procedure.

Knowing that the first FIP setting has a BECC=256 bytes and the secondsetting has a BECC=512 bytes, means, for example, that the secondsetting can correct an impulse that causes twice as many bit errors asthe first FIP setting. On the other hand, the first FIP setting has lessFEC parity (overhead) which results in a higher information (net) datarate for the user during Showtime. This is also illustrated by the factthat K, the number of information bytes per code word, is higher for thefirst FIP setting. For each of the FIP settings, the receiver detectswhether there are bit errors after the decoding and deinterleavingprocess. This detection can be done by, for example, by performing acyclic redundancy check (CRC) after the decoding and deinterleavingprocess is complete as defined in the ITU standard G.992.x. In general,the CRC is a well-known method for detecting bit errors. Since impulsenoise occurs at random times, this system can operate using a particularFIP setting for a period of time that is sufficient to encounter theimpulse noise. In the simple example illustrated above, only the K and Rvalues were modified. It should be appreciated however, that the systemsand methods of this invention are not limited thereto but rather can beextended to include the modification of any one or more FIPparameter(s).

The process of determining the impact of impulse noise by transmittingand receiving using a plurality of FIP settings can be done while insteady-state transmission, i.e., Showtime for DSL systems, when userinformation bits are being transmitted.

The process of determining the impact of impulse noise by transmittingand receiving using a plurality of FIP settings, can be done during aspecial impulse noise training period during which the system is notactually transmitting user data. In accordance with this exemplaryaspect of the invention, the standard xDSL procedure is modified toinclude the capability of measuring the effectiveness of a chosenimpulse noise protection (INP) setting during initialization and havingreceiver-controlled updates of transmission parameters that control theINP setting, e.g., FEC parameters and interleaving parameters, duringinitialization.

A new initialization state is included in the xDSL initializationprocedure that provides the capability to measure the effectiveness ofthe current INP settings. The new initialization state will be referredto as the INPTraining state and it can, for example, follow the exchangeof the Showtime transmission parameters such as the bi/gi table, trelliscoding, tone reordering, FEC/interleaving parameters, etc. It isimportant to note that steady-state transmission during which userinformation is transmitted is known as “Showtime” in XDSL systems andthat standard ITU G.992.3 ADSL systems and ITU VDSL G.993.3 systemsinclude an exchange phase in initialization during which the Showtimeparameters are exchanged, see, for example, G.992.3 and G.993.1.

During this INPTraining state, the transceivers transmit and receiveusing at least one of the standard Showtime functions using the Showtimeparameters, e.g., bi/gi table, FEC/interleaving parameters, etc., thatare exchanged during the previous exchange phase. These functionsinclude at least one of Showtime PMD functions, e.g., bi/gi table,trellis coding, tone reordering, etc., PMS-TC functions, such as framingand FEC/interleaving, and TPS-TC functions. During the INPTrainingstate, the TPS-TC can transmit idle ATM cells, HDLC flags, or 64/65 idlepackets depending on the TPS-TC type.

At the receiver, the CRC, the FEC, the TPS-TC error detectioncapabilities, and other receiver functions can be used to determinewhether the INP setting is adequate for the current impulse noiseconditions on the line. The receiver can also use these receiverfunctions to automatically and dynamically determine what the correctINP setting should be. If the current INP setting is not adequate, a newset of Showtime transmission parameters can be exchanged and the processrepeated by reentering the INPTraining state using the newly exchangedShowtime transmission parameters. If, on the other hand, the current INPsetting is adequate, the transceivers can enter into Showtime.

An exemplary advantage associated with this aspect of the invention isthat the receiver can measure the effectiveness of the current INPsetting and can make updates to the INP setting based on thesemeasurements during initialization. This is important because thereceiver generally has the most knowledge of channel conditions,receiver functionality, and processing capability. In general, thereceiver has the best capability to make the necessary trade offsbetween data rate, latency, excess margin, FEC redundancy, coding gain,and the like. Current related ADSL systems have the operator servicinglines that are experiencing high impulse noise by trying various INPsettings in an attempt to find an error-free operating mode. However,since the operator is not capable of making the receiver trade offsstated above, such as the data rate, latency, and the like, the processwill often lead to a sub-optimum result.

Another exemplary aspect of this invention relates to determining thelength and/or repetition period of impulse noise events in order toselect an appropriate INP setting.

For example, the transceivers can transmit and receive using at leastone of the standard Showtime functions and parameters such as the bi/gitable, FEC/interleaving parameters, and the like. These functionsinclude the Showtime PMD functions, such as the bi/gi table, trelliscoding, tone reordering and the like, PMS-TC functions (such as framingand FEC interleaving) and TPS-TC functions. The TPS-TC may transmit ATMcells, HDLC packets, or 64/65 packets depending on, for example, theTPS-TC type.

At the receiver, the CRC, the FEC, the TPS-TC error detectioncapabilities, and other receiver functions can be used to determine thelength and the period of the impulse noise and whether an INP setting isadequate for the current impulse noise conditions on the line.

For example, the receiver can determine the length of an impulse noiseevent. The length of impulse noise events can be determined in a numberof ways. For example, they can be determined as:

-   -   1. The length of the impulse in time, e.g., how many        microseconds the impulse power is above a specific noise level        (e.g. the above the stationary channel noise)    -   2. The number received bits that are affected by the impulse        noise, e.g. how many received bits are in error in a specific        sliding time window or how many consecutive bits are in error in        a stream    -   3. The number of received ATM cells that are affected by the        impulse noise, e.g. how many ATM cells contain bits that are in        error. This may be detected using a standard ATM HEC, which is a        CRC that covers the ATM header bits. Alternatively this may        detected by checking the ATM payload bits by, for example,        transmitting a predefined bit pattern that is known by the        receiver    -   4. The number of 64/65 packets that are affected by the impulse        noise, e.g. how many packets contain bits that are in error (the        64/65 CRC can be used for this)    -   5. The number of received DMT symbols that are affected by the        impulse noise, e.g., the measured noise in a DMT symbol is above        a predefined threshold which results in most (if not all) the        bits in that DMT symbol being in error    -   6. The number of FEC codewords that are affected by the impulse        noise, e.g., how many codewords have an uncorrectable number of        bit errors, i.e., the number of bit errors in a codeword exceeds        the number of bit that are correctable by the FEC code

In accordance with one exemplary aspect, the FEC correction capabilityand interleaving is turned off when trying to determine the length ofthe impulse noise. For example, the FEC may be configured so that thereare no parity bits (i.e., R=0) or the FEC may be disabled altogether(i.e., no codewords are sent). Additionally, for example, theinterleaving may be disabled by setting the interleaver depth to 1(i.e., D=1). Disabling the FEC and interleaving is beneficial whentrying to determine the length of the impulse noise based on affectedbits, affected code words and/or affected packets. This is true sincewhen the FEC/interleaving is enabled, the impulse noise event will bespread over a large time period and it will be more difficult todetermine the length of the original impulse.

The exemplary techniques discussed herein that are used to determine thelength of the impulse event can also be extended to determining therepetition period of the impulse noise event, i.e., how often is impulsenoise occurring. The repetition period can be important, because theperiod has an effect on the FIP setting that is used. For example, ifthe interleaving spreads an impulse noise event over a period of timethat exceeds the impulse period, then the interleaver could combinemultiple impulse noise events together. As a result, the FEC correctioncapability may have to be increased. In order to determine therepetition period of an impulse noise event, the receiver can firstdetect the impulse noise event as discussed above and then determine howoften the impulse noise events occur. For example, periodic impulsenoise due to AC power lines occurs at a 120 Hz reception rate, orapproximately every 8 ms.

In the case where the impulse noise does not have a fixed length, i.e.,where the impulse noise varies over time, the receiver can attempt todetermine the maximum impulse noise length. This involves measuringseveral impulse noise events and determining the impulse noise eventwith the maximum length. In practice, it is likely that the impulsenoise will have varying length and it is important that theFEC/interleaving settings be configured to handle the maximum, e.g.,worst case, impulse noise event.

Once the receiver determines the (maximum) length of the impulse noiseand/or the repetition period of the impulse noise, this information canbe sent to the transmitting modem. In particular, when the receivingmodem, such as a Customer-Premises (CPE) modem determines the (maximum)length of the impulse and/or the repetition period of the impulse, theCPE modem could send the information to a Central Office (CO) modem in amessage. The length of the impulse length event can be defined andspecified in the message in terms of time, received bits, ATM cells,64/65 packets, DMT symbols, or the like. The CO modem could then, forexample, provide this information to the CO-MIB, which is the managementinterface that is used by the operator or service provider to configurethe modems. For example, based on this information, the operator mayconfigure the modems to a different INP value, data rate, latency, orthe like. This process could also be automated such that the messagereceived by the CO modem allows automatic reconfiguration to adjust, forexample, INP values, data rate, latency, or the like.

The exemplary aspects of the invention that are used to determine thelength and/or repetition period of the impulse noise event can beperformed during initialization and/or Showtime. During initialization,the method can perform during an INPTraining state such as the onedescribed herein. During Showtime the method can be performed, forexample, during a Showtime INP adaptation phase as described herein.

These and other features and advantages of this invention are describedin, or are apparent from, the following description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of this invention will be described in relation to thefigures, wherein:

FIG. 1 is a functional block diagram illustrating an exemplary impulsenoise adaptation system according to this invention;

FIG. 2 illustrates an exemplary initialization state machine thatincludes an INPTraining state according to this invention;

FIG. 3 is a flowchart outlining an exemplary method for impulse noiseprotection adaptation during Showtime according to this invention;

FIG. 4 is a flowchart illustrating an exemplary receiver optimizedmethod for impulse noise protection adaptation according to thisinvention;

FIG. 5 is a flowchart illustrating an exemplary method for forward errorcorrection synchronization according to this invention;

FIG. 6 is a flowchart illustrating an exemplary method for flag signalsynchronization according to this invention; and

FIG. 7 is a flowchart illustrating an exemplary method for determiningimpulse noise length and period according to this invention.

DETAILED DESCRIPTION

The exemplary embodiments of this invention will be described inrelation to adapting impulse noise parameters as well as measuringimpulse noise length and repetition period within an xDSL environment.However, it should be appreciated that, in general, the systems andmethods of this invention can be applied and will work equally well withany type of communication system in any environment.

The exemplary systems and methods of this invention will be described inrelation to xDSL modems and associated communication hardware, software,and communication channels. However, to avoid unnecessarily obscuringthe present invention, the following description omits well-knownstructures and devices that may be shown in block diagram form orotherwise summarized.

For purposes of explanation, numerous details are set forth in order toprovide a thorough understanding of the present invention. It should beappreciated however, that the present invention may be practiced in avariety of ways beyond the specific details set forth herein. Forexample, the systems and methods of this invention can generally beapplied to any type of system within any environment in which theimpulse noise length and/or period is desired, or for which impulsenoise adaptation is desired.

Furthermore, while the exemplary embodiments illustrated herein show thevarious components of the system collocated in specific locations, it isto be appreciated that the various components of the system can belocated or relocated at distant portions of a distributed network, suchas a telecommunications network and/or the Internet, or within adedicated secure, unsecured and/or encrypted system. Thus, it should beappreciated that the components of the system can be combined into oneor more devices, such as a modem, or collocated on a particular node ofa distributed network, such as a telecommunications network. As will beappreciated from the following description, and for reasons ofcomputational efficiency, the components of the system can be arrangedat any location within a distributed network without effecting theoperation of the system. For example, the various components can belocated in a central office (CO or ATU-C) modem, a customer premisesmodem (CPE or ATU-R), or some combination thereof. Similarly, thefunctionality of the system could be distributed between one or more ofthe modems and an associated computing device.

Furthermore, it should be appreciated that the various links, includingcommunications link 20, connecting the elements can be wired or wirelesslinks, or any combination thereof or any other known or later-developedelement(s) that is capable of supplying and/or communicating data to andfrom the connected elements. The term module as used herein can refer toany known or later-developed hardware, software, or combination ofhardware and software that is capable of performing the functionalityassociated with that element. Furthermore, as used herein, the term“transmitter” has the same meaning as the term “transmitting modem” or“transmitting transceiver” and the term “receiver” has the same meaningas “receiving modem” or “receiving transceiver.”

FIG. 1 illustrates an exemplary embodiment of an impulse noiseadaptation system 100 according to an exemplary embodiment of thisinvention. In particular, the system 100 comprises a receiving modem 200and a transmitting modem 300. The exemplary receiving modem 200comprises a decoder/deinterleaver 210, a bit error rate (BER) detectionmodule 220, a forward error correction and interleaving parameter (FIP)module 230, an impulse noise length determination module 240, an impulsenoise period determination module 250, an impulse noise parametermanagement module 260, an impulse noise protection adaptation module270, a synchronization module 280, a message module 290 and a controllerand memory (not shown) all interconnected by a link 5. The exemplarytransmitting modem 300 comprises a management module 310, asynchronization module 320, a message module 330, and may optionallyinclude an impulse noise parameter management module 340.

In operation, the exemplary communication system adapts the impulsenoise parameters on-line by operating using a series of different FIPsettings. For each FIP setting, the system can dynamically determine ifthe appropriate amount of impulse noise protection is being provided.Based on these determinations, the system can select a particular FIPsetting for regular, i.e., Showtime, operation. As will be discussed ingreater detail hereinafter, this impulse noise protection adaptation canbe performed during Showtime and/or during initialization.

Impulse noise protection adaptation during Showtime includes thefollowing exemplary steps. First, the DSL system, i.e., the transmittingand receiving modems, completes regular initialization and commencestransmission and reception using a first FIP setting. For DSL systems,this first FIP setting is selected by the receiver 200 and is based onthe minimum/maximum data rate, maximum latency, and minimum INPparameters as configured by, for example, the service provider via themanagement module 310. A detailed explanation of this procedure can beseen in G.992.3.

The system will use this first FIP setting for a period of time T1.During this period, and in conjunction with the BER detection module220, the receiver 200 detects if bit errors have occurred using thisfirst FIP setting for the decoding and deinterleaving performed by thedecoder/deinterleaver 210. For example, the receiver 200 can use a CRCto detect bit errors. If there are no bit errors, then the current INPsetting is adequate and there is no need to modify the INP setting andShowtime communication can continue as normal.

However, if bit errors have been detected by the BER detection module220, an adjustment to the INP setting may be appropriate. For example, aservice provider, a user, or the system can choose an updated INPsetting. Since bit errors have been detected, the INP setting could beincreased by an on-line modification to the FIP parameters.Specifically, the transmitter 300, and for example the management module310, in response to an indication from the receiver 200 that bit errorshave been detected, can send a message to the receiver 200 to initiate achange in the INP settings. The receiver 200, in cooperation with themessage module 290, the FIP module 230, the impulse noise parametermanagement module 260 and impulse noise protection adaptation module270, can return a message to the transmitter 300 that specifies a newlydetermined FIP setting that satisfies the new INP requirement.

The transmitter 300 and receiver 200 can then transition to the new INPsetting by starting to use the new FIP parameters for transmission andreception, respectively, at a synchronized point in time. Thissynchronization can be done in accordance with a number of exemplarymethods that are discussed hereinafter.

Upon synchronization, the system 100 continues communication using theupdated FIP settings for a second period of time T2. If the receiverdetects that bit errors are occurring using this updated FIP settingduring the decoding and deinterleaving performed by thedecoder/deinterleaver 210 the steps can be repeated with the selectionof another updated INP setting. However, if there are no bit errorsdetected by the receiver 200 during the time period T2, then the new INPsetting is adequate and there is no need for further change at whichpoint the INP adaptation procedure can end.

This Showtime-based INP adaptation process can be repeated as many timesas necessary until an INP setting is obtained that provides the requiredimpulse noise immunity and/or bit error rate.

One advantage of this technique is that the transition between differentFIP settings can be accomplished without reinitializing the transceiversusing the lengthy standard initialization procedure that is typicallyused in ADSL and VDSL systems. In contrast, the transition can occurwithout the standard initialization since the transition between FIPsettings can be synchronized between the transmitter and the receiversuch that the receiver 200 can determine when to start FEC decodingusing the new FIP settings for K and R. As will be discussedhereinafter, this transition can be synchronized using a number ofdifferent exemplary methods.

The transition can also be accomplished without synchronization in whichcase the receiver 200 will determine when the new FIP settings are usedby some alternative means. For example, the receiver could determinewhen the new FIP settings are being used by FEC decoding using both theold and updated FIP settings and determining which one is currentlybeing utilized by the transmitter by determining with which FIP settingthe codeword is correct. Other receiver functions such as CRCs, ATM HECerrors and the like could also be used.

This impulse noise protection adaptation procedure can be performedduring regular steady-state transmission, i.e., Showtime in ADSL, usingactual user data or, for example, idle ATM cells. This methodology canalso be performed during a special impulse noise training period duringwhich the system is not actually transmitting user data. For example,this impulse noise training period could utilize transmitted predefinedpseudorandom bit streams or, for example, idle ATM cells or HDLC flagsfor determining an appropriate INP value.

The length of the time periods T1, T2, . . . can be controlled by, forexample, the receiving modem 200. The receiving modem 200 could controlthe length of these time periods by, for example, sending a message thatspecifies how long the transmitter should transmit using a particularFIP setting. This length can be defined, for example, in terms of thenumber of DMT symbols or the number of FEC codewords. For example, amessage could indicate that 200 DMT symbols should be sent for all FIPsettings or 300 FEC code words should be sent for all FIP settings.Alternately, the message can indicate a different number of DMT symbolsor FEC code words for each FIP setting. This technique could further beused to aid in determining an appropriate INP setting by forwarding apredetermined number of DMT symbols at a first FIP value, followed by asecond number of DMT symbols at a second FIP value, and so on. For eachof these sets of DMT symbols and associated FIP values, the receivercould determine the bit error rate, with the cooperation of the BERdetection module 220, and then forward a message, with the cooperationof the message module 290, to the transmitter 300 specifying which FIPsetting provided the appropriate impulse noise protection.

Similarly, the transmitting modem 300 and receiving modem 200 couldcooperate such that an optimum impulse noise protection value isconverged upon. For example, the transmitting modem 300, with thecooperation of the message module 330, could forward a message to thereceiving modem 200 specifying a first INP setting. If there are no biterrors, a message could be sent via the message module 290 to thetransmitting modem 300 indicating that there are no bit errors and alower INP value could be attempted. The impulse noise parametermanagement module 260 and FIP module 230 could then determine anappropriate lower INP setting and forward it to the transmitter 300. Asdiscussed above, since a lower INP value is inversely proportional tothe user data rate, it is advantageous to optimize the INP value basedon detected errors. The transmitting modem 300, in cooperation with themessage module 330, could then send another message to the receivingmodem 200 indicating that the lower INP value will be transitioned to atwhich point the procedure repeats itself through detection of bit errorsin cooperation with the bit error rate detection module 220 and thedecoder/deinterleaver 210. This reduction in the INP parameters cancontinue until bit errors are detected at which point a message is sent,with the cooperation of the message module 290, to the transmittingmodem 300 indicating a higher INP value is required since bit errorswere detected. Then, for example, based on an evaluation of aconvergence of bit errors vs. impulse noise protection parameters, anoptimum INP value can be determined and transitioned to by the receiver300 and transmitter 200. This procedure could also be used to increasethe INP parameters in a similar fashion.

The length of the time periods T1, T2, . . . can also be controlled bythe transmitter 300. For example, the transmitter 300 could control thelength of these time periods, by, for example, sending a message to thereceiver 200 that specifies the length of time the transmitter willtransmit using a particular FIP setting. This length could be defined interms of the number of DMT symbols or, for example, the number of FECcodewords. The exemplary message could indicate that, for example, 200DMT symbols would be sent for all FIP settings or 300 FEC codewords willbe sent for all FIP settings. The message could also indicate adifferent number of DMT symbols or FEC codewords for each FIP setting.In general, the message could contain any type of information relatingto how long the transmitter will be using a specific FIP setting(s).

The length of the time periods T1, T2 . . . can also be controlled by,for example, a service provider or a user. For example, the serviceprovider could configure through the management module 310 a minimumtime X=10 seconds to be used for testing each FIP setting. The serviceprovider could use the knowledge of the nature of the impulse noise,such as how often impulse noise event occurs, to determine the times.However, and in general, the length of the time periods could beconfigured to be any length of time as appropriate.

As discussed above, when a determination is made that there are biterrors and an increase in the INP setting is desirable, the receivingmodem 200 can determine the new INP settings. However, it should beappreciated that the transmitting modem 300, in cooperation with theimpulse noise parameter management module 340 could also determineupdated INP settings. For example, either modem could continually adaptthe INP values as discussed above until no bit errors that are theresult of impulse noise are detected by the BER detection module 220.

As alluded to above, the receiver and transmitter can synchronize themodification of the FEC and interleaving parameters such that the boththe transmitter and receiver start using the parameters at the sameinstant in time. This synchronization can be based on, for example, asynchronization using FEC codeword counters or a flag signal.

For synchronization using FEC codeword counters, the receiver 200 andtransmitter 300 can synchronize the change in cooperation with the syncmodules 280 and 320, by counting the FEC codewords from the beginning ofShowtime and the transition would occur when a specific FEC codewordcounter value that is known by both the transmitter 300 and the receiver200 is reached. Prior to the transition point, the transmitter 300 orreceiver 200 in cooperation with the message module 290 and messagemodule 330, would send a message indicating the FEC codeword count valueon which the FIP parameters will be updated. For example, thetransmitting modem 300 can enter into Showtime and the synchronizationmodule 320 commences counting the number of transmitted FEC codewords.For example, the first codeword transmitted has a count value of 0, thesecond transmitted codeword has a count value of 1. . . . The countercan optionally be defined as having a finite length, for example, 0 to1023 (10 bits) such that when the value of 1023 is reached, on the nextFEC code word that is transmitted, the counter restarts at the value of0.

Similarly, the receiving modem 200 upon entering Showtime starts acounter in cooperation with the synchronization module 280 that countsthe number of received FEC codewords. The first received FEC codewordhas a count value of 0, the second received FEC codeword to the countvalue of 1. . . . As with the synchronization module 320, thesynchronization module 280 can have a counter with a finite length, forexample 0-1023, such that when the value of 1023 is reached, on the nextFEC codeword the counter restarts at 0.

At some point, for example, based on detected bit errors, the user, aservice provider, or the like, it is determined that an updated FIPsetting is needed. The receiving modem 200 can send a message, via themessage module 290, to the transmitting modem 300, and in particular themessage module 330 and impulse noise parameter management module 340.The updated FIP setting can alternatively be sent from the transmittingmodem to the receiving modem.

The synchronization module 280 and message module 290 then cooperate tosend a message to the transmitting modem 300 specifying the FEC codewordcounter value on which the new FIP settings are to be used fortransmission and reception. Alternatively, the transmitting modem, incooperation with the message module 330, can send a message to thereceiving modem indicating the FEC codeword counter value on which theFIP settings are to be used for transmission and reception. For example,the message can indicate that when the code word counter equals 501, thenew FIP setting will be used for transmission and reception.

When the transmitter FEC codeword counter equals the value indicated inthe message, the synchronization module 220 instructs the transmittingmodem 300 to transition to the new FIP settings. Similarly, when thesynchronization module 280 in the receiving modem 200 counts the FECcodeword that equals the value indicated in the message, the receivingmodem 200 transitions to using the new FIP settings for reception.

Synchronization can also be performed through the use of a flag signal(sync flag). For this exemplary embodiment, the receiving modem 200 andtransmitting modem 300, in cooperation with the synchronization module280 and synchronization module 320, synchronize the change in FIPsettings using a flag or marker signal that is similar to that used inthe ADSL2 G.992.3 ORL protocol. This protocol may be more desirable thanusing an FEC codeword counter because, for example, it has greaterimpulse noise immunity.

For synchronization using a flag signal, the receiver and transmitterwould start using updated FEC and interleaving parameters on apre-defined FEC codeword boundary following the sync flag. For example,while transmitting using a first INP setting, a determination is madeby, for example, the BER detection module 220 that a new FIP setting isneeded due to the presence of impulse noise on the line. Thisdetermination can be performed by the receiving modem, in cooperationwith the FIP module 230, the transmitting modem, a user, a serviceprovider, or the like. The receiving modem 200, in cooperation with themessage module 290, sends a message to the transmitting modem 300indicating the new FIP settings to be used for transmission andreception. Alternatively, the transmitting modem, in cooperation withthe message module 330, prepares and sends a message to the receivingmodem indicating the updated FIP settings to be used for transmissionand reception.

The transmitting modem then sends a flag or marker signal to thereceiving modem 200 indicating that the new FIP settings are to be usedon a predetermined number of DMT symbols following the transmission ofthe flag or marker signal. For example, the flag signal could be aninverted sync symbol, or sync FLAG, as used in the ADSL2 G.992.3 OLRprotocol. The transmitting modem 300 then starts using the new FIPsettings for transmission on the predetermined number of DMT symbolsfollowing the transmission of the flag or marker signal. Similarly, thereceiving modem starts using the new FIP settings for reception once thepredetermined number of DMT symbols following the receipt of the flag ormarker signal have been received.

EXAMPLE 1 On-Line INP Adaptation FIP Setting

This section describes an example of FIP settings for On-Line INPadaptation for DSL. In this example only the number of information bytesin a codeword (K) and the number of parity bytes in a codeword (R) areupdated on-line. The Codeword Size (N) and Interleaver Depth (D) are notchanged. This means that the latency (and interleaver memory size) andthe line rate are not modified on-line. Since N=K+R this placesrestrictions on the allowed values for K and R.

-   1st Setting—{Approximate User Data Rate=3.968 Mbps, Line Rate=4.096    Mbps, N=128, K=124, R=4, S=1, D=64, Latency=16 msec, INP=1}-   2nd Setting—{Approximate User Data Rate=3.840 Mbps, Line Rate=4.096    Mbps, N=128, K=120, R=8, S=1, D=64, Latency=16 msec, INP=2}-   3nd Setting—{Approximate User Data Rate=3.584 Mbps, Line Rate=4.096    Mbps, N=128, K=112, R=16, S=1, D=64, Latency=16 msec, INP=4}

The On-line INP adaptation process is restricted to only modify thenumber of information bytes in a codeword (K) and the number of paritybytes in a codeword (R). The FEC Codeword Size (N=K+R) and InterleaverDepth (D) are not changed. This means that the latency (or interleavermemory size) and the line rate are not modified on-line. However theuser data rate will change during the process since K is being modified.Also since the line rate and the FEC codeword size are not modified, theS value does not change in the process. It is important to note thatwith these constraints, the On-line INP adaptation process can be donein as seamless manner (no bit errors and service interruption). Thismeans provided that the modification if the FIP setting is restricted toK and R, the transition between FIP settings can be done in a seamlessmanner. This is the case because if the codeword size N and theinterleaver depth D are not modified, the transition can happen withoutthe problem of “interleaving memory flushing.” Interleaver memoryflushing is a well-known problem in which errors occur becauseinterleaver and deinterleaver memory locations are overwritten due toon-line changes in the codeword size (N) and or interleaver depth (D).

EXAMPLE 2 On-Line INP Adaptation FIP Setting

This section describes an example of FIP settings for On-Line INPadaptation for DSL. In this example only the Codeword Size (N) and thenumber of parity bytes in a codeword (R) are updated on line. The numberof information bytes in a codeword (K) and Interleaver Depth (D) are notchanged and therefore the user data rate does not change. This meansthat the latency (and interleaver memory size) and the line rate aremodified on-line. Since N=K+R this places restrictions on the allowedvalues for K and R.

-   1st Setting—{Approximate User Data Rate=3.968 Mbps, Line Rate=4.096    Mbps, N=128, K=124, R=4, S=1, D=64, Latency=16 msec, INP=1}-   2nd Setting—{Approximate User Data Rate=3.968 Mbps, Line Rate=4.224    Mbps, N=132, K=124, R=8, S=1, D=64, Latency=16 msec, INP=2}-   3nd Setting—{Approximate User Data Rate=3.968 Mbps, Line Rate=4.480    N=128, K=124, R=16, S=1, D=64, Latency=16 msec, INP=4}

In this example the Line Rate is modified on-line. For this reason it isnecessary to also complete a rate adaptation process in order tocomplete this On-Line INP adaptation. A method for Seamless RateAdaptation is described in U.S. Pat. No. 6,498,808.

While these examples restrict the changes to a subset of the FIPparameters, they can obviously be extended to cover any combination ofthe FIP parameters (N, K, R and D). For example, the value of D couldalso be modified in addition to the values of K, R and N. This couldresult in a change in the required interleaver memory and latency. Inorder to keep the memory and latency constant it is necessary to changethe codeword size (N) accordingly when changing the interleaver depth(D). For example, if the interleaver depths is changed from D=64 toD=128, the Codeword size would have to be decreased by a factor of 2 sothat overall latency is constant.

FIG. 2 illustrates an exemplary modified initialization state machinethat includes the INPTraining state prior to Showtime. This statemachine is based on the VDSL G.993.1 ITU standard. As defined inG.993.1, VTU-O is the VDSL Transceiver Unit at the Optical Network Unit(ONU) and VTU-R is the VDSL Transceiver Unit at the Remote terminal. TheInitialization state machine in FIG. 2 is an example of how INPTrainingstates could be included in a modified VDSL initialization procedure.While exemplary FIG. 1 includes the INPTraining state at a specific timein the initialization sequence, the INPTraining state can be included atany time during initialization provided that it is preceded by a stateduring which Showtime parameters are exchanged between the transceivers.

O-P-INPTrain

During the O-P-INPTrain State the VTU-O transmitter transmits DMTSymbols using the standard PMD, PMS-TC and TPS-TC SHOWTIME functionswith parameters exchanged during the previous Exchange Phase. Duringthis state, the TPS-TC transmits idle ATM cells, HDLC flags or 64/65idle packets. SOC is inactive during this state.

This state is used by the VTU-R to determine the correct DS INP settingbased on Impulse Noise conditions on the line. For example, thedownstream CRC, FEC error detection, TPS-TC error detectioncapabilities, and other receiver functions can be used to determinewhether the INP setting is adequate. The receiver can also use thesereceiver functions to determine the correct INP setting.

If the VTU-R determines that the current INP setting is not adequate,the VTU-R transmits the R-P-ISYNCHRO2 signal to indicate the need totransition back to the Exchange Phase in order to exchange newtransmission parameters.

If the VTU-R determines that the current INP setting is not adequate,the VTU-R transmits the R-P-SYNCHRO2 signal to indicate that it is OK totransition to Showtime with the current transmission parameters.

R-P-INPTrain

During the R-P-INPTrain State the VTU-R transmitter transmits DMTSymbols using the standard PMD, PMS-TC and TPS-TC Showtime functionswith parameters exchanged during the previous Exchange Phase. Duringthis state, the TPS-TC transmits idle ATM cells, HDLS flags or 64/65idle packets. SOC is inactive during this state.

This state is used by the VTU-O to determine the correct US INP settingbased on Impulse Noise conditions on the line. For example, the upstream(US) CRC, FEC error detection, TPS-TC error detection capabilities, andother receiver functions can be used to determine whether the INPsetting is adequate. The receiver can also use these receiver functionsto determine the correct INP setting.

If the VTU-O determines that the current INP setting is not adequate,the VTU-O transmits the O-P-ISYNCHRO2 signal to indicate the need totransition back to the Exchange Phase in order to exchange newtransmission parameters.

If the VTU-O determines that the current INP setting is not adequate,the VTU-O transmits the O-P-SYNCHRO2 signal to indicate that it is OK totransition to Showtime with the current transmission parameters.

O-P-SYNCHRO2

The O-P-SYNCHRO2 is the same as defined in the current VDSL1. As inVDSL1, the VTU-O transmitter enters Showtime after transmitting theO-P-SYNCHRO2 signal.

But, if the VTU-R has not also entered into Showtime, the VTU-O waitsfor receipt of the R-P-SYNCHRO2 or R-P-ISYNCHRO2. If the VTU-O receivesthe R-P-SYNCHRO2 it continues in Showtime. If the VTU-O receives theR-P-ISYNCHRO2, the VTU-O transmitter transitions back to the beginningof the O-P-MEDLEY state.

R-P-SYNCHRO2

The O-P-SYNCHRO2 is the same as defined in the current VDSL1. As inVDSL1, the VTU-R transmitter enters Showtime after transmitting theR-P-SYNCHRO2 signal.

But, if the VTU-O has not also entered into Showtime, the VTU-R waitsfor receipt of the O-P-SYNCHRO2 or O-P-ISYNCHRO2. If the VTU-R receivesthe O-P-SYNCHRO2 it continues in Showtime. If the VTU-R receives theO-P-ISYNCHRO2, the VTU-R transmitter transitions back to the beginningof the R-P-MEDLEY state.

O-P-ISYNCHRO2

The O-P-ISYNCHRO2 is phase-inverted version of the O-P-SYNCHRO2, i.e., asubcarrier-by-subcarrier 180 degrees phase reversal. The VTU-Otransmitter transitions to the beginning of the O-P-MEDLEY state aftertransmitting the O-P-ISYNCHRO2 signal.

R-P-ISYNCHRO2

The R-P-ISYNCHRO2 is phase-inverted version of the R-P-SYNCHRO2, i.e., asubcarrier-by-subcarrier 180 degrees phase reversal. The VTU-Rtransmitter transitions to the beginning of the R-P-MEDLEY state aftertransmitting the R-P-ISYNCHRO2 signal

Exemplary Overview State Transition Rules Based on SYNCHRO2 and theISYNCHRO2 signals:

-   -   If either the VTU-O or the VTU-R transmits the ISYNCHRO2 signal        then both VTU-R and VTU-O transition back to beginning of the        MEDLEY state.    -   If both the VTU-O and the VTU-R transmit the SYNCHRO2 signal        then both the VTU-R and the VTU-O transition into Showtime.

There are several important points regarding this exemplary embodiment.First, the receiver can measure the efficiency of the plurality of INPsettings without completing a new initialization procedure such as isused in ADSL and VDSL systems. Second, the length of the time of theO-P-INPTrain and R-P-INPTrain states can be controlled by the VTU-R andVTU-O respectively. In this way the receivers have adequate time todetermine if the current INP setting is correct. In order to accomplishthis, prior to entering the R-P-INPTrain state, the VTU-O can transmit amessage to the VTU-R indicating the minimum length of the R-P-INPTrainstate. Likewise, prior to entering the O-P-INPTrain state, the VTU-R cantransmit a message to the VTU-O indicating the minimum length of theO-P-INPTrain state. For example, the message could indicate that aminimum of 20000 DMT symbols should be sent during the O-P-INPTrainstate. Additionally, the length of the time of the O-P-INPTrain andR-P-INPTrain states could be set by the DSL service provider in order tomake sure that the initialization does not take too long or because theservice provider may have some knowledge of the statistics of theimpulse noise which require setting the length of the INPTrain states.In this exemplary case a message could be sent from the VTU-O to theVTU-R indicating the minimum and/or maximum length of the O-P-INPTrainand/or the R-P-INPTrain states. For example, the message could indicatethat a minimum of 20000 DMT symbols should be sent during theR-P-INPTrain state. Also, for example, the message could indicate that amaximum of 40000 DMT symbols should be sent during the R-P-INPTrainstate.

The length of the time of the O-P-INPTrain and R-P-INPTrain states couldalso be controlled by the VTU-O and VTU-R respectively. In this case,the transmitters will have control of the state lengths. In order toaccomplish this, prior to entering the R-P-INPTrain state, the VTU-R cantransmit a message to the VTU-O indicating the minimum length of theR-P-INPTrain state. Likewise, prior to entering the O-P-INPTrain state,the VTU-O can transmit a message to the VTU-R indicating the minimumlength of the O-P-INPTrain state. For example, the message couldindicate that a minimum of 20000 DMT symbols should be sent during theO-P-INPTrain state.

As discussed above, another exemplary aspect of this invention relatesto determining the length and/or repetition period of impulse noiseevents in order to select an appropriate INP setting.

The INP length can be determined using any one of a plurality ofmetrics. For example, the INP length can be determined based on one ormore of:

-   -   1) The length of the impulse in time    -   2) The number of received bits that are affected by the impulse        noise    -   3) The number of received ATM cells that are affected by the        impulse noise    -   4) The number of 64/65 packets that are affected by the impulse        noise    -   5) The number of received DMT symbols that are affected by the        impulse noise    -   6) The number of FEC codewords that are affected by the impulse        noise

As an example, assume that length of the impulse noise is 700microseconds (Example 1). At a data rate of 1 Mbps this could correspondto an impulse noise length of 700 bits (Example 2) assuming that allimpulse noise was high enough to affect all 700 bits in the 700microsecond period. This also could correspond to a impulse noise lengthof 700/(53*8)=1.65 ATM cells since there are 53 bytes in a ATM cell(Example 3). This also could correspond to an impulse noise length of700/(65*8)=1.35 64/65 packets since there are 65 bytes in a 64/65 packet(Example 4). This also could correspond to an impulse noise length of700/(250)=2.8 DMT symbols (INP=2.8) assuming the DMT symbol rate is 4kHz (250 microseconds DMT symbol length) (Example 5).

As an example, the determination of the INP length with the number ofreceived bits that are affected by impulse noise can be performed inaccordance with the following procedure. Initially, the transmittingmodem 300 transmits data using at least one of the Showtime functions.In accordance with a first exemplary embodiment, at least the bitallocation table is used. In addition, or alternatively, the trelliscoder, framer, and TPS-TC functions may also be used. Additionally, oralternatively still, the interleaving and FEC may also be used.

The receiving modem 200 receives data using at least one of the Showtimefunctions, such as the bit allocation table as discussed above.Similarly, the trellis coder, framer, TPS-TC and/or interleaving and FECcan be used.

The transmitter 300 then transmits a predefined bit pattern that is usedfor determining or measuring the impulse noise length based on detectederroneous bits. The receiving modem 200 compares, with the assistance ofthe impulse noise length determination module 240, the predefined bitpattern to the received bit pattern in order to detect bit errors. Sinceimpulse noise events typically cause a burst of errors in a bit stream,the receiving modem 200 determines the length of the impulse noise eventby detecting and determining the length of the error burst.

Once the receiver 200 determines the length of the impulse noise, thereceiving modem 200, in cooperation with the message module 290, sends amessage to the transmitter 300 that indicates the determined length ofthe impulse noise.

In accordance with an exemplary embodiment, the FEC correctioncapability and interleaving is turned off when trying to determine thelength of the impulse noise, e.g., R=0 and D=1. Disabling the FEC andinterleaving is beneficial when trying to determine the length of theimpulse noise based on affected bits, affected code words, or affectedpackets. This is the case because if the FEC/interleaving is enabled,the impulse event can be spread over a large time period which makes itmore difficult to determine the length of the original impulse.

The exemplary methodology discussed above can also be used to determinethe length of the impulse event using other metrics. For example, apredefined bit pattern could be used in the payload of the ATM cells orthe 64/65 packets. Idle packets or cells, which carry a predefinedpattern, could also be used. In these cases, the receiver would comparethe received data to the predefined data to determine the length of theimpulse or to determine if an INP setting is adequate. Alternatively,the CRC of the ATM cell or 64/65 packet could be used to determine thelength of the impulse noise. This would provide a courser measurement ofthe impulse noise length since it would be an integer number of packetsor cells. In this example, a 700 bit impulse would cause CRC errors intwo ATM cells so the length of the impulse noise would be two ATM cells,as opposed to the more precise measurement of 1.64 above. Likewise, inthis example, a 700 bit impulse would cause CRC errors in two 64/65packets so the length of the impulse noise would be two packets, asopposed to the more precise measure of 1.35 above.

Likewise, a predefined bit pattern could also be used to modulate thecarriers in the DMT symbols so that the receiver would know what DMTsymbols were transmitted. In this case, the receiver 200 would determinehow many DMT symbols were corrupted by comparing the received signalwith a known transmitted signal.

The exemplary techniques used to determine the length of the impulsenoise event could also be extended to determine the repetition rate ofthe impulse noise event in cooperation with the impulse noise perioddetermination module 250. In order to determine the repetition period ofan impulse noise event, the receiver 200 detects the impulse noise eventas discussed above and then determines how often they occur. Forexample, periodic impulse noise due to AC power lines occur at 120 Hzreception rates or approximately every 8 ms. The receiver 200 could, forexample, also store information about past impulse noise events andcompare detected impulse noise events to historical events. The impulsenoise period determination module 250 could then determine which eventsof a similar duration are occurring at what interval. This informationcould then be used in determining an appropriate INP setting.

Once the receiver 200 determines the (maximum) length of the impulseand/or the repetition period of the impulse, the information, with thecooperation of the message module 290 can be sent to the transmittingmodem. For example, when the receiving modem 200 determines the(maximum) length of the impulse and/or the repetition period of theimpulse, the impulse noise period determination module 250, incooperation with the message module 290 can forward information to thetransmitting modem that quantifies this period. The transmitting modem300 could provide this information to, for example, the managementmodule 310, that would allow, for example, an operator or serviceprovider to configure the modems. For example, based on the periodinformation contained in the message, the operator may configure themodems to different INP values, data rates, latency, or the like.

The receiver 200 could also test a specific INP setting by detecting howmany received bits are errored in a specific time period. For example,if the specific INP setting enables the correction of 100 bits in an 8msec. time period then the receiver 200 could detect how many bits areerrored in a sliding 8 msec. window. If less than 100 bits are detectedin error in the 8 ms sliding window, then the INP setting is adequate.

If more than 100 bits are detected in error in a sliding window, thenthe INP setting is not adequate, and the FEC/interleaving needs to bechanged to provide more error correction capability.

Likewise, instead of using the received number of bits that are effectedby the impulse noise, the receiver could test a specific INP setting bydetecting how many received ATM cells, 64/65 packets, DMT symbols,and/or FEC corrections are affected in a specific time period.

FIG. 3 outlines an exemplary method for performing impulse noiseprotection adaptation during Showtime according to this invention. Inparticular, control begins in step S300 and continues to step S310. Instep S310, traditional DSL initialization occurs. Next, in step S320,Showtime is entered between the two modems using the first FIP settingthat was determined during the initialization in step S310. Then, instep S330, a determination is made whether bit errors are occurringusing the first FIP setting. If bit errors are not occurring, controlcontinues to step S340 where the control sequence ends. Otherwise,control jumps to step S350.

In step S350, a determination is made that an increase of the INPsetting is required that requires modification of the FIP parameters.Next, in step S360, updated INP parameter is determined and a messageforwarded to the receiver specifying the new INP setting. Then, in stepS370, the receiver forwards to the transmitter updated FIP parametersfor the new impulse noise protection requirements. Control thencontinues to step S380.

In step S380, the transmitter and receiver transition to using theupdated INP parameters at a synchronization point. Next, in step S390Showtime operation continues. Control then continues back to step S330.

FIG. 4 outlines an exemplary method for receiver optimized impulse noiseprotection adaptation during Showtime. In particular, control begins instep S400 and continues to step S410. In step S410, the DSL systemcompletes regular initialization In particular, control begins in stepS400 and continues to step S410. In step S410, the DSL system completesstartup initialization and continues into Showtime in step S420 using afirst FIP setting. Control then continues to step S430 where adetermination is made whether bit errors are occurring using the firstFIP setting. If bit errors are not occurring, control continues to stepS440 where the control sequence ends.

Otherwise, control jumps to step S450 where the receiver increases theimpulse noise protection by modifying the FIP parameters. Next, in stepS460, a synchronization point is determined between the transmitter andreceiver, and when the synchronization point is reached both thetransmitter and the receiver transition to the updated FIP setting instep S470 and Showtime communications continue and control returns backto step S430.

FIG. 5 illustrates an exemplary method for synchronization of themodified FEC and interleaving parameters according to this invention. Inparticular, control begins in step S500 and continues to step S510. Instep S510, the transmitter enters Showtime and counts the number oftransmitted FEC codewords. Next, in step S520, the receiver entersShowtime and counts the number of received FEC codewords. Then, in stepS530, after a determination is made that an updated FIP setting isneeded, the receiving modem sends a message to the transmitting modemindicating a new FIP setting that is to be used for transmitting andreception or, alternatively, the transmitting modem sends a message tothe receiving modem indicating the new FIP setting to be used fortransmission and reception. Control then continues to step S540.

In step S540, a message with the FEC codeword counter value on which thenew FIP values are to be used is exchanged. Next, in step S550, adetermination is made whether the counter value has been reached at thetransmitter. If the counter value has not been reached, the nextcodeword is counted in step S560 and control continues back to stepS550.

Otherwise, if the counter value has been reached, control jumps to stepS570. In step S570, the transmitter transitions to the new FIP setting.Next, in step S580, a determination is made whether the counter valuehas been reached at the receiving modem. If the counter value has notbeen reached, the next received FEC codeword is counted in step S585 andcontrol continues back to step S580. However, when the counter value hasbeen reached in the receiving modem, control jumps to step S590 wherethe receiving modem switches to the new FIP value. Control thencontinues to step S595 where the modems continue Showtime communicationand control continues to step S597 where the control sequence ends.

FIG. 6 illustrates an exemplary method of synchronization using a flagsignal according to this invention. In particular, control begins instep S600 and continues to step S610. In step S610, the modems enterShowtime using the first FIP parameters. Next, in step S620, a messageis exchanged indicating the new FIP settings. Then, in step S630, thetransmitter forwards to the receiver a flag signal indicating when thenew FIP settings are to be used.

At step S640, and at a predefined change time following the transmissionof the flag signal, the transmitter begins transmission using the newFIP parameters. Next, at step S650, at the predefined change timefollowing the reception of the flag signal, the receiver commencesreception utilizing the new FIP parameters. Control then continues tostep S660 where Showtime communication continues with the controlsequence ending at step S670.

FIG. 7 illustrates an exemplary method of impulse noise length andperiod determination. In particular, control begins in step S700 andcontinues to step S710. In step S710, the transmitter transmits datausing at least one Showtime function. Next, in step S720, the receiverreceives data using at least one Showtime function. Then, in step S730,the transmitter transmits predefined information to the receiver.Control then continues to step S740.

In step S740, the receiver receives the predefined information from thetransmitter. Next, in step S750, the receiver compares the receivedpredefined information to the predefined information and determines thedifferences (i.e., errors) between the two. Then, in step S760, andbased on the detected errors, the length of the burst error isdetermined. Next, in step S770, a message is forwarded to thetransmitter indicating the length of the impulse noise event. Controlthen continues to step S780 where a determination is made whether theperiod of the impulse noise event is also to be determined. If theperiod is not to be determined, control continues to step S790 where thecontrol sequence ends. Otherwise, control jumps to step S800.

In step S800, and once the length of the impulse noise event is know,the receiver detects how often the impulse noise events occur. Forexample, historical information regarding the length and timing ofprevious impulse noise events can be stored in a memory (not shown).Then, a comparison can be made with the aid of a processor (not shown)to compare an impulse noise event to the historical information todetermine the period of repetition (if any) of similar impulse noiseevents and, for example, a message indicating the period as well as thetiming forwarded to, for example, another transceiver, the CO, or ingeneral any destination as appropriate. Thus, in a similar manner, thisinformation can be forwarded in step S810 to, for example, thetransmitter in a message specifying the repetition frequency of theimpulse noise event. Control then continues to step S820 where thecontrol sequence ends.

The above-described system can be implemented on wired and/or wirelesstelecommunications device(s), such a modem, a multicarrier modem, a DSLmodem, an ADSL modem, an xDSL modem, a VDSL modem, a linecard, testequipment, a multicarrier transceiver, a wired and/or wirelesswide/local area network system, a satellite communication system, amodem equipped with diagnostic capabilities, or the like, or on aseparate programmed general purpose computer having a communicationsdevice.

Additionally, the systems, methods and protocols of this invention canbe implemented on a special purpose computer, a programmedmicroprocessor or microcontroller and peripheral integrated circuitelement(s), an ASIC or other integrated circuit, a digital signalprocessor, a hard-wired electronic or logic circuit such as discreteelement circuit, a programmable logic device such as PLD, PLA, FPGA,PAL, modem, transmitter/receiver, or the like. In general, any devicecapable of implementing a state machine that is in turn capable ofimplementing the methodology illustrated herein can be used to implementthe various communication methods, protocols and techniques according tothis invention.

Furthermore, the disclosed methods may be readily implemented insoftware using object or object-oriented software developmentenvironments that provide portable source code that can be used on avariety of computer or workstation platforms. Alternatively, thedisclosed system may be implemented partially or fully in hardware usingstandard logic circuits or VLSI design. Whether software or hardware isused to implement the systems in accordance with this invention isdependent on the speed and/or efficiency requirements of the system, theparticular function, and the particular software or hardware systems ormicroprocessor or microcomputer systems being utilized. Thecommunication systems, methods and protocols illustrated herein howevercan be readily implemented in hardware and/or software, or any means,using any known or later developed systems or structures, devices and/orsoftware by those of ordinary skill in the applicable art from thefunctional description provided herein and with a general basicknowledge of the computer and telecommunications arts.

Moreover, the disclosed methods may be readily implemented in software,that can be stored on a storage medium, and executed on programmedgeneral-purpose computer, a special purpose computer, a microprocessor,or the like. In these instances, the systems and methods of thisinvention can be implemented as a program embedded on personal computersuch as JAVA® or CGI script, as a resource residing on a server orcomputer workstation, as a routine embedded in a dedicated communicationsystem or system component, or the like. The system can also beimplemented by physically incorporating the system and/or method into asoftware and/or hardware system, such as the hardware and softwaresystems of a communications transceiver.

It is therefore apparent that there has been provided, in accordancewith the present invention, systems and methods for impulse noiseadaptation. While this invention has been described in conjunction witha number of embodiments, it is evident that many alternatives,modifications and variations would be or are apparent to those ofordinary skill in the applicable arts. Accordingly, it is intended toembrace all such alternatives, modifications, equivalents and variationsthat are within the spirit and scope of this invention.

The invention claimed is:
 1. A method, in a transceiver, comprising:transmitting using a first interleaver parameter value; transmitting aflag signal; and changing to transmitting using a second interleaverparameter value that is different than the first interleaver parametervalue, wherein the second interleaver parameter value is used fortransmission on a pre-defined forward error correction codeword boundaryfollowing transmission of the flag signal.
 2. The method of claim 1,wherein the flag signal is an inverted sync symbol.
 3. The method ofclaim 1, wherein the change in interleaver value does not cause biterrors or service interruption.
 4. The method of claim 1, wherein thechange in interleaver value is associated with at least one of animpulse noise protection value, a data rate and a latency value.
 5. Themethod of claim 1, wherein the change in interleaver value is associatedwith a service provider configuration.
 6. The method of claim 1, furthercomprising transmitting the flag signal on a telephone line thatexperiences impulse noise from external sources including one or more ofAM radio, HAM radio and AC power lines.
 7. The method of claim 1,wherein the transceiver is located in a linecard that includes amanagement interface that is usable by an operator or service providerto configure a service.
 8. A device comprising: an interleaverconfigured to interleave a plurality of bits; and a transmitter portioncoupled to the interleaver and configured to: transmit using a firstinterleaver parameter value; transmit a flag signal; and change totransmitting using a second interleaver parameter value that isdifferent than the first interleaver parameter value, wherein the secondinterleaver parameter value is used for transmission on a pre-definedforward error correction codeword boundary following transmission of theflag signal.
 9. The device of claim 8, wherein the flag signal is aninverted sync symbol.
 10. The device of claim 8, wherein the change ininterleaver value does not cause bit errors or service interruption. 11.The device of claim 8, wherein the change in interleaver value isassociated with at least one of an impulse noise protection value, adata rate and a latency value.
 12. The device of claim 8, wherein thechange in interleaver value is associated with a service providerconfiguration.
 13. The device of claim 8, wherein the transmitter isfurther configured to transmit the flag signal on a telephone line thatexperiences impulse noise from external sources including one or more ofAM radio, HAM radio and AC power lines.
 14. The device of claim 8,wherein the transmitter is located in a linecard that includes amanagement interface that is usable by an operator or service providerto configure a service.
 15. The device of claim 8, wherein thetransmitter is located in a Customer Premises Equipment (CPE) thatincludes a management interface that is usable by an operator, a serviceprovider or service user.
 16. The device of claim 8, wherein thetransmitter includes at least one digital signal processor.
 17. Thedevice of claim 8, wherein the transmitter includes at least one ASIC(Application-Specific Integrated Circuit).